1. Field of the Invention
The present invention relates to a resin composition capable of forming a high-precision pattern using an electron beam or extreme ultraviolet rays, which is suitably used in an ultramicrolithography process such as a process for manufacturing a super-LSI or a high-capacity microchip, and other photofabrication processes, and a pattern forming method using the same. Specifically, the present invention relates to a resin composition which can be suitably used in a process using a substrate having a specific undercoating film, and an actinic ray-sensitive or radiation-sensitive film, mask blanks, and a pattern forming method, each using the same. In addition, the present invention relates to a method for manufacturing an electronic device including the pattern forming method, and an electronic device manufactured by the method.
2. Description of the Related Art
In microfabrication using a resist composition, along with the increase in the degree of integration of integrated circuits, there is a demand for formation of ultrafine patterns. Therefore, the exposure wavelength also tends to become shorter, as in the case of the transition from g-line to i-line, or further to excimer laser light, and for example, the development of lithographic technologies using electron beams is currently underway. Further, as a resin used for the exposure to excimer laser light such as that of a KrF excimer laser, a resin having a structure where a hydrogen atom of a phenolic hydroxyl group is substituted with a group having an aliphatic hydrocarbon residue, a resin having a structure where the hydrogen atom is substituted with a group having an aryl group, a resin having a structure where the hydrogen atom is substituted with an alkyl group, and a resin having a structure where the hydrogen atom is substituted with a linear alkyl group, to which an oxirane group is introduced, are described, respectively, in JP2000-29220A, JP3546687B, JP1995-295220A (JP-H07-295220A), and JP1989-293338A (JP-H01-293338A).
In order to form ultrafine patterns, thickness reduction of the resist is required; however, if a thinner resist is formed, dry etching resistance is decreased. To cope with the thickness reduction of the resist, there has been proposed, for example, a resin formed by immersing methylol urea in a methacrylic resin (JP2012-31233A and JP2012-46731A), but sufficient dry etching resistance has not been obtained.
Furthermore, in the field of electron beam lithography, the influence of electron scattering in the resist film (forward scattering) has been reduced in recent years, by increasing the acceleration voltage of the electron beam (EB). However, in this case, the resist film has a reduced electron energy trapping ratio which decreases the sensitivity, and the effect of scattering (backward scattering) of electrons reflected in the resist substrate increases. In particular, when forming an isolated pattern having a large exposure area, the effect of backward scattering is large and the resolution properties of the isolated pattern are impaired.
Particularly, in the case of patterning on photomask blanks used for semiconductor exposure, a light-shielding film containing heavy atoms is present as the layer below the resist, and the effect of backward scattering attributable to the heavy atoms is serious. Therefore, in the case of forming an isolated pattern on photomask blanks, among others, the resolution properties are highly likely to decrease.
As one of the methods to solve these problems, use of a resin having an aromatic skeleton such as naphthalene (for example, JP2008-95009A and JP2009-86354A) and use of a resin containing an oxirane group (for example, JP2011-123225A) are being studied, but the problem regarding the resolution properties of an isolated pattern is unsolved. Further, it is found that for the technology disclosed in JP2011-123225A, dry etching resistance is not sufficient. In JP2005-99558A, as one of the methods to enhance the resolution properties of an isolated pattern, a resin containing a group for adjusting the solubility is used, but it has not approached a satisfactory level in the resolution properties of an isolated pattern.
Also, the microfabrication using a resist composition is not only used directly to produce an integrated circuit but has also been applied, in recent years, to the fabrication or the like of a so-called imprint mold structure (see, for example, JP2008-162101A and Basic and Technology Expansion Application Development of Nanoimprint—Fundamental Technology of Nanoimprint and Latest Technology Expansion, edited by Yoshihiko HIRAI, Frontier Publishing (issued June, 2006)). Therefore, it has become an important task to satisfy high sensitivity, high resolution properties (for example, a high resolution, an excellent pattern shape, and a small line edge roughness (LER)), and good dry etching resistance all at the same time, and this needs to be solved.